Dynamoelectric machine



March 29, 1949. M. P WgNTHER ErAL 2,465,982

DYNAMOELECTRI C MACHINE Filed Sept. 1:5, 1945 3 Sheets-Sheet l A5 A@ 4/ FIG. 37 7 39 l .Z .mmf/414. Q vx, g." we w March 29, 1949. M. P, wlNTHER ETAL 2,465,982

DYNAMOELECTRIC MACHINE Filed Sept. 13, 1945 I5 ShetS-Sheet 2 u l l L lL l sgg/ wa/@WWW March 2.9, 1949.

Filed sept. 15, 1945 FIGA.

M. P. wxNTHER ET AL 2,465,982

DYNAMOELECTRI C MACHINE 3 Sheets-Sheet, 3

F'ORMU LATION OF AREAS DETERMINE A2 BYTRQUE AND SPACE RcQumEMeNTs, ALLQWNG to scam. oF A2 FOR EACH H.P. HEAT LOSS EXPECTED.

SLIP SPEED Patented 29, 1949.

DYNAMOELECTBIC MACHIN E Martin P. Winther, Waukegan, lll., and Anthony Winther, Kenosha, Wis., assignors to said Martin P. Winther, 'as trustee Application September 13, 1945, Serial No. 61.6.122

1Claim.

This invention relates to dynamoelectric ma-` chines, and with regard to certain more specific features, to eddy-current slip couplings, brakes, dynamometers and the like.

Among the several objects of the invention may be noted the provision of a dynamoelectric machine for clutches, brakes, d ynamometers and the like in which is obtained a torque-speed curve which is flatter over a wider speed range than heretofore; the provision of a machine of the class described which within wide speed limits will generate or transmit torque in substantial proportion to magnetic excitation; the provision of a machine of this class which on the torquespeed curve has a very steep rising torque characteristic under initial slip speed conditions, whereby is left an increased length for the ilat portion of the curve; and the provision of a machine of this class which requires no relatively movable regulating means to bring about said improvements. Other objects will be in part obvious and in part pointed out hereinafter.

'I'he invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exempliiied in the structures hereinafter described, and the scope of the application of which will be indicated in the following claim.

In. the accompanying drawings, in which several of various possible embodiments of the invention are illustrated,

Fig. 1 is a longitudinal section of typical apparatus embodying the invention;

Fig. 2 is a right-hand elevation of Fig. l but showing only the field member;

In 2,106,542 is shown means for overcoming drooping torque characteristics of older machines (note curve II as compared to curve I in Fig. 8 of that patent). In 2,220,007 and in 2,367,636 are shown diierent means tending to flatten a curve of the character of curve II in Fig. 8 of 2,106,542. Patent 2,367,636 shows the simplest of the lastmentioned means and consists in employing belts of pole-forming teeth on opposite sides of an exciting coil, the adjacent ends of the teeth overlapping the coil and to some extent overlapping one another peripherally. 'I'he present invention is a. further improvement upon the construction of said 2,367,636 patent in which the curve b of Fig. 10 in said patent is very greatly flattened in its operating range and which has a much steeper initial portion by extending the range of the flatness, and which has a much sharper knee portion. In Fig. 5 herein comparisons between the curves O-l and N--2, or between N-I and N2 illustrate the dierences which will be discussed in detail hereinafter.

Referring now more particularly to Fig. l, there is shown at numeral l a drive shaft which may be connected to a suitable power unit such as a motor or the like. Attached to this shaft is a hub 3 having a peripheral portion 6 to which is bolted a flange member 'I. Together the parts 5 and 1 form a groove 3 for holding an annular eld coil Il. This field coil is excited from a suitable circuit supplied from a suitable slip-ring circuit (not shown). The character of slip-ring circuits for energizing eld coils of this nature is so well-known that further description in this respect is unnecessary. The parts 5 and 1 form a grooved field coil container ring having a U- shaped cross section. The inside or cylindric base part of the U-shape is indicated at 9 and the sides or iianges are indicated at I3 and I5.

From the side flanges I 3 and I5 extend interdigitated pole-forming teeth I1 and I 9, respectively. These teeth I'I and I9 have root portions connected with the ring parts I3 and I5. Their ends are alternately directed over the outside of the coil II which they overlap. These overlapping portions of teeth II and IS are indexed 2| and 23, respectively. The tooth p0r- -tions 2| and 23 overlap the coil and they overindicated in Fig. 3, they are of'tapered forms with long contiguous edges between them. They ex tend entirely over the coil il and extend beyond it. Further particulars in regard to the teeth are ven below. giMounted on bearings 2i on the hub 3 is a hub 21 of a driven memberl. The latter is formed with suitable V-shaped grooves 3i for V belts I3 by means of which power may be taken from the Within the member 2l are constructed fan blades Il for cooling purposes. The periphery of the member l! is attached by welding or the like to an inductor or armature ring or drum Il.

` Around this drum is located ring u nem by keying means 3l and a suitable fit. Member ll is not necessarilyv made of the highly magnetic material of which member 31 is made, the latter to be described. Parts 8l, I! and Il rotate as a unit with member 2l. Between the outsides of the teeth I1 and il and the inner relatively smooth cylindric surface of the drum 31 is an air gap G which is made as smallas may be consistentwith maintaining proper mechanical clearances both under cool and hot conditions.

'nie advantages of the invention are obtained by properly relating the forms of the inductor ring 31. teeth I1 and il. The materials of which these parts are made are also of some importance, particularly as to the inductor. They should be of high magnetic permeability and low electrical resistance. This is particularly true of the in- -ductor ring. Por the purpose, magnetic ingot- `is not detrimental but it is not necessary. 'Ihe electrical resistance is of the order of six times the electrical resistance of. pure copper. It should be of a value of to 16 kilogausses under a magnetomotive force 8" of 21 gilberts per centimeter.

' v The reason for the importance of the above type of iron, in the inductor 31 particularly. is that it should be very easy to magnetize to a high degree and still readily lose its magnetism when the magnetizing force is removed.

Another and important feature of the invention, for obtaining the desired results. refers to the form of the magnetic circuit around the coil il. The field around the coil Vil is generally speaking of toric drape as illustrated by the dash lines in Fig. 1. As indicated in Figs. 2 and 3,

' tapered alternate north .and south polar teeth I'I and Il point oppositely. The marks N and S indicate north and south polarities respectively.

Hence when there is relative movement between the polar teeth and the inductor 31, induced north and south Dolar regions sweep through given areas in the inductor.

Atthemediansectionofthecoil il theseN and B regions are of about equal effect and introduce torque properties analogous to an ordinary salient pole inductive machine, that is. a steeply 55 pected (see I'ig.A 4).

. 4 or sides of the coil il north and Ysouth pole characteristics dominate, depending on the side under consideration. For example, in Fig. 3 it will be seen that toward the right, north pole character- 16 inductive eifect in the inductor 31 over the center of the coil Il is most like that of a salient pole machine, gradually toward the opposite ends of the coil the inductive eiects become more like (but not the same) vas those of a toothed rotor 15' type of machine as in Patent 2,106,542. How- `\ever, there is a diiference in the present construction, due to the alternate extensions of the teeth 2i and 23 being carried substantially across the axial'length of coil il, so that even in or near 20 the planes at the ends of the coil l I there is some tendency toward reversal of neld in the inductor 31. However, this reversal is not complete, as is the case in the central plane of the coil. In the planes adjacent the coil ends one or the other of the north or south polarities preponderates (in Fig. 3 the north polarity on the right and the south polarity on the left) From the above it is clear that in the central plane of the coil Il the alternating north and 3b south polar areas of v flux emanating from the teeth Il and Il are about equal in effect. In the planes at or near the sides of the coil Il the alternate north and south effects of the teeth are present but their torque effects upon the in- `5 ductor are diiferent. 'Ihis alternating north and south polar effect varies in effect from the central plane of the coil to the planes next to the coil ends. Thus the new effect is produced as indicated in Pig. 5.

40 The forms of the field member and inductor should preferably be as indicated in Figs. 1 and 4,

' to which thefollowing comments are directed:

near the inner cylindric surface of the inductor Il. The insides of these teeth slope away from the coil Il as indicated at numerals Il (for teeth i1) and 2l (for teeth Il). This has the eifect of additionally tapering the teeth toward their ends. The total of the outer areas A: of the teeth ll and Il in said imaginary cylinder is determined arbitrarily, for example, by allowing approximately ten square inches .of this outer tooth area for each horsepower of heat loss ex- Then the actual area Aa: DxrxWXJI; where D is the outside diameter of said imaginary cylinder through the outsides oftheteeth Iland Il andWisthe effective in This effective widthw isbetween the endsoftheteeth. The smallendsofthe teeth liein y. It will be seen from the equation'for area Azthatitisineifecttheareaofacircular 0f width L. Width L (Fig. 3) should be approximately20to35timestheairgapG(Fig.1).

In Fig. 3 the arrows-fran the character Az.

indicate the bounding edges for one pair of the essentially triangulariignres that go to make risingtorque-speed curve. Toward the axialends up the area A: but it is to Ybe understood that widthoftheteethinthiscylinderasindicatednains isthe'sumoiallsuchilguresaroundthedeld. considered the included angles between i' the essential triangles forming the isOasshowninFig. 3. Thisprovides he wide bases shown making these triangles practically eiuilateral.

With the area A: obtained by proper choice ofDandW,theareaofthesectionAsthrough the bottom of groove l in Fil. 1 isto equal .3xAs.

This areaAJ is the circular-sectional area of the U-shaped form 1 for retaining the coil Il. Also, eachofareasAsandAaaretobeequaltoAs. Ar'eas A4 and An' are-*the areas of the sections indicated in Fig. 1. Area As is the circular right sectional area oi the inductor drum l1. A4 is the sum of the areas through the large bases of either set of teeth I1 or Il. This area Aa is calculated at about the place where the teeth curve down at their connections with circular parts Il and il, respectively.

Area As=.l8xA, being the total of the areas of each set of teeth l1 or Il taken at what will be called the root of the poles which is the sum of these areas in a plane passing substantially through one side of the coil il.

Equivalent relationships arising from those given above appear in the chart of Fig. 4.

It may be noted that one-half of the area A: (Fig. 3) is the sectional area of the eil'ective magnetic air gap of one-half of the poles, that is. of one set of poles. either north or south. This means that the area A: is

where is the effective area Just mentioned. Also. by the same reasoning Thus it is clear that the magnetic path through the iiux gap is of greater cross section than the magnetic path through the metal parts of the magnetic circuit indicated at As. A4. As and Aa. But, although it may seem that, on the average, the outer surfaces of the polar teeth next to the inductor drum 31 are not operated at said ux saturation, still, since there are some smaller parts of north poles peripherally adjacent to larger parts of south poles and vice versa, there is a variation in unit density at a givenvpoint on a pole surface which aids in producing the desired eiIect.

A slip coupling built along the above lines has a much iiatter torque-speed curve as indicated in Fig. 5. In this Fig. curve O-l is typical for the older type of machine operating cool without the invention. Curve 0 2 is typical of a comparable machine operating cool but built along the lines of the invention. Curve N-I is typicalof an older class of machine operating hot without the invention; and curve N-2 is typical of a comparable machine operating hot and built under the invention. The dlierence is at once apparent. Curves 0-2 and N-2 have much steeper initial portions and much flatter.

`longer fiat portions with sharp knees between the steep-and fiat portions. This eiiect is substantially independent of the machine temperature.

'Y of the reverse as shown in the drawings.

It will be understood that the inductor member of the combination may be the driving element and the field member the driven element, instead It is also to be understood that' either one of the elements may be held stationary while the other is turned in order to apply torque to the former, as for example in the case of a dynamometer or brake application of the invention.

Applications wherein the invention has value arefor example in clutches for tension drives in various processes; electric clutch drives for gun sighting; for reversing controls of airplane wings and tail surfaces; ventilating blowers. etc. In many of these applications the desired requirement is that of a torque curve which has a very steep initial rising characteristic of torque versus slip speed and which thereafter bends very sharply and remains virtually flat in the remaining range of the slip speed. In the dat part of such a curve the slip will be about inversely proportional to the magnetization of the field coil.

It is to be understood that although we show the coil il 'excited from an outside electrical source for producing a magnetic condition in the polar teeth i1 and Il, this coil may be omitted by making the annular iield member of permanently magnetic material, such as for example the well-known Alnico" metal (Fig. s). 'Ihis is accomplished by substituting for the coil Il a torus Il of said permanently magnetic Alnico or similar material. In this case the member 4I itself acts as a source for the toric magnetic circuit and also this ring 43 is held clamped in place between cheeks Il and l1 of magnetic material from which extend the magnetic teeth 4I and Il corresponding generally in shape to the ones above described. The ring Il is held clamped between the cheeks by brass studs il.

In Fig. 6 it will be understood that the support for the iield member is the shaft Il which corresponds to shaft I in Fig. 1. The inductor drum is numbered $1 (corresponding to inductor drum Il in Fig. 1). This drum i1 is mounted on a rotary support 59 (corresponding to the member 2l in Fig. 1). Further elaboration of the Fig. 6 alternative will not be necessary in view of the description already given in respect to the preierred form of the invention. It should, however, be noted in Fig. 6 that the toric field, indicated by the dash lines, is completed in part through the permanent annular magnet 4l. The section of this annular magnet should preferably be arranged so that the optimum magnetic areas are obtained as above described.

It should be understood in regard to both forms of the invention that while the stated areas are important many of the advantages of the invention are attained by the use of other areas, the primary feature being that the polar teeth extend substantially entirely across the annular field ,member and are tapered in opposite directions.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

Dynamoelectric apparatus comprising relatively rotary driving and driven members, one of said members consisting of an inductor member havinl v. substantially uninterrupted homogeneous eddy-current inductor surface, the other member comprising an annula'rly formed held-producing member producing l. toroidl ilux neld interlinkinz said field and inductor members. magnetic poles closely enveloping the vannulrly formed tleld member and carrying said toroidal flux field. sold poles being formed with oppositely directed mterdmmed pour teeth extending between the' l0l ileld member and the inductor member, said teeth being formed substantially as alternately extending equilatersl triangles lying adjacent to the inductor member.

ANTHONY WINTHER.

MARTIN P. WINTHER. l'

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Prince May 28, 1946 

